The primary aim of this research is to delineate regulatory features of the ovary as they relate to the action of gonadotropins and/or prostaglandins. In this coming period we propose: 1. To determine the primary structure of the rat luteal LH receptor. 2. To raise antibodies against it to investigate the subunits composition and biosynthesis of the LH receptor. 3. To purify the luteal coupling proteins Ns and Ni responsible for transmission of the signal generated by occupancy of LH and FSH receptors into altered rates of cyclic AMP formation, and to determine the properties of these N proteins as they compare to N proteins from other tissues. 4. To purify, if possible, biologically active LH receptors and study their coupling to luteal, as well as other, Ns proteins. 5. To perform a comparative study on the structure of LH receptors in luteal, follicular and Leydig cell tissues. 6. To delineate the genomic organization of LH receptor gene(s) and their possible homologies to other receptor genes. 7. To initiate studies on the effects of PGF2alpha and oxytocin on the expression of oxytocin-like peptides and LH receptor in regressing luteal tissue. The information gained and the tools developed through this research will contribute significantly in the definition of the role of LH receptors in the regulation of ovarian functions and may aid in development of new type of contraceptives.